A smart card means a chip card having a microprocessor or a smart card controller. Within this invention, in general, if a smart card has a plurality of microprocessors and/or controller circuits and/or logic circuits etc, the microprocessor etc, that makes the main functions of the smart card to be controllable, is referred to as microprocessor or smart card controller. Any microprocessors, controllers, logic circuits etc, by which the secondary functions of the smart card are controllable, are referred to as e.g. system controller or control logic.
From DE 198 41 886 C2 a method and a processor chip card for generating one-time passwords are known, as well as a method for the authentication of a user using a one-time password. For computing a first password, a randomly selected initial value is selected as plaintext to be encrypted, the initial value being encrypted with an encryption function fk and a key k. All subsequent one-time passwords are calculated by once more applying the encryption function fk to the preceding one-time password, i.e. the preceding one-time password serves as a plaintext for the next one-time password. As to be able to produce different one-time passwords and series of one-time passwords for different users, the encryption function fk is parameterized with the secret key k of the user of the processor chip card, which is used for the encryption. As to authenticate a user by the computer of an authenticating authority, the computer of the authenticating authority can determine the currently valid one-time password of each user and associate it to the user. The user transmits his currently valid one-time password to the computer of the authenticating authority, which compares the one-time password to the one-time password determined by the computer and authenticates the user only when the two one-time passwords match.
DE 198 41 886 C2 also describes the use of such a one-time password and authentication method in connection with a chip card, in particular a Eurocheque card having a chip in which the secret key k of the user is stored who is the holder of the Eurocheque card. An alternative use described in DE 198 41 886 C2 provides that as said chip card a chip card inserted in a mobile phone is used, the mobile phone being used as a reading device for the chip card.
In U.S. Pat. No. 6,067,621 a further apparatus and a further method for generating one-time passwords is described, as well as a method for the authentication of a user. There, a secret key for generating one-time passwords is stored on the IC card of a user. A portable terminal of the user reads the secret key out of the IC card, generates a random number and generates a one-time password using the read out secret key and the generated random number. The generated one-time password can be displayed on a display of the portable terminal. For generating a different one-time password in the terminal a different random number is generated and used. For authenticating the user, the user transmits the one-time password generated in his portable terminal to a server. The server likewise has the secret key and the random number of the user at its disposal, computes the one-time password itself, compares the self-computed one-time password to the one-time password obtained from the user and authenticates the user when the two one-time passwords match.
The apparatuses described in DE 198 41 886 C2 and U.S. Pat. No. 6,067,621 use a separate terminal having a display as a reading device for the chip card used when generating the password, as to display the generated one-time password. With the apparatus and method of U.S. Pat. No. 6,067,621, moreover, the terminal is necessary for computing the one-time password. With that the two known apparatuses have the disadvantage, that the terminal always has to be carried along. This makes the handling of the apparatuses complicated.
One-time passwords are used, for example, for secure electronic payment transactions, e.g. credit transfers, while home banking via Internet. The one-time password in this connection is referred to as transaction number (TAN). For carrying out a secure electronic payment transaction, e.g. an online credit transfer via Internet, the holder of a personal account, in particular bank account, initiates the payment transaction at a credit institution by e.g. making entries in an electronic credit transfer form, and electronically transmitting the electronic credit transfer form to the credit institution. In order to the payment transaction being executed, it has to be acknowledged with a transaction number (TAN). The transaction numbers (TANs) to be used usually are sent by post to the holder of the personal account (account holder) in the form of paper lists. The account holder electronically transmits a transaction number (TAN) from the list to the credit institution. With that the account holder acknowledges the payment transaction and thus effects that the payment transaction is executed. If the TAN list of an account holder comes into the hands of an unauthorized person, e.g. by the unauthorized person intercepting the list sent by post, and the unauthorized person gets knowledge of the access identification key for online banking (home banking), he can make payment transactions from the personal account of the account holder.
In the technical field of electronic purses it is already known to provide smart cards (microprocessor chip cards), the smart card controller (microprocessor) of which serves as a purse chip having the function of an electronic purse, with a display with the help of which the credit balance can be displayed in the purse chip. The problem with these smart cards having a display is that the electricity consumption of said smart card controllers is very high. But, however, it is necessary that the credit balance is displayed on the display so long that a user can read it off the display without problems.
DE 100 35 094 A1 describes a smart card having a smart card controller, a memory, a display, a system controller (display control logic, control logic) for the display, and an energy source (e.g. battery). The memory can be operated independent of the smart card controller with the help of the system controller (display control logic). The smart card controller is used as a purse chip of an electronic purse and contains an electronic credit balance, which via a terminal (chip card reading device) is reduced and increased by transactions. By a credit transfer transaction from a bank account to the purse chip, the credit balance of the purse chip is increased. By a credit transfer transaction from the purse chip to an external bank account or an external electronic money storage, the credit balance of the purse chip is reduced. The contacting between the chip card and the terminal is effected e.g. via contacts adapted for contact-type contacting. The smart card controller, which has a considerably higher electricity consumption than the system controller (display control logic) for the display, is supplied with energy via the external terminal. Since during the usage of the smart card controller, i.e. e.g. for increasing or reducing the credit balance in the purse chip, the terminal and the chip card are already connected to each other, it is no additional effort to supply the smart card controller with energy via the terminal. Whereas the system controller and the display are supplied with energy via the internal energy source of the smart card. Data from the smart card controller, for example the credit balance of the electronic purse, which are to be displayed on the display, are stored in the memory, as long as the smart card is connected with the terminal. Then the data can be displayed on the display using the internal energy source and with the aid of the display control logic, without a terminal being required for that.
A further smart card designed as an electronic purse and having a display for displaying the credit balance of the electronic purse is described in WO 03/030396 and DE 101 47 140 A1.